Lowering my stock lwb

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I plan on lowering my 71 lwb using 2 1/2 lowering spindles but I'm not sure what to use for the rear. Sould I use 2 inch lowering blocks or go for 2 inch lowered springs. Now, I do use my truck going to the dump or hauling stuff. I want to keeep the load from sagging the bed. I do take it cars shows aroung here and keep it in good shape but I sometimes have to use it otherwise. So any help will be greafull. It is a stock height.